I can confirm that as of June 30, 2024, that piano at C17 is still there (made the trek from T2 after arriving earlier than expected — as a bonus, got to go through the psychedelic Rhapsody in Blue tunnel on my way there).
As you can see from the photo, the placement of the piano itself was not what I would call conducive to playing if I value my physical safety, so I snapped a photo and went back to my own gate. Hope you had a safe flight @ShiroKuro!